Recall the case of the rental car fleet owner who suspects that the mean annual mileage of his cars is greater than the national mean of 12,000 miles. He selects a random sample of n = 225 cars and calculates the sample mean to be x = 12,375 miles and the sample standard deviation to be s = 2,415 miles. Determine the level of statistical significance and P-value for this hypothesis test, and interpret your findings.